


It's Just You and Me Now

by Fukae_Flwr83



Category: Swapfell - Fandom, Undertale (Video Game)
Genre: Alternate Universe - Swapfell (Undertale), Biting, Blow Jobs, Dom/sub, Ecto-Penis (Undertale), Ecto-Tongue (Undertale), F/M, Fingerfucking, Implied/Referenced Cheating, Kinky, Minor Sans (Undertale)/Reader, Mutt teases, My First Smut, Penis In Vagina Sex, Plot What Plot/Porn Without Plot, Reaader has a vagina, Reader CHEATS, Reader Is Not Chara (Undertale), Reader Is Not Frisk (Undertale), Reader and Mutt do the Nasty, Rough Sex, Sans is gone so the Mutt will play, Swapfell Papyrus (Undertale), Swapfell Sans (Undertale), Voice Kink, cheating warning, first time writing any kind of smut, lots of fucking, mention of masturbation, possible open relationship, reader is a secret pervert, reader is a shy kinky perv, reader/sans - Freeform, reader/swapfall papyrus
Language: English
Status: In-Progress
Published: 2019-03-05
Updated: 2019-03-05
Packaged: 2019-11-12 07:22:58
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,835
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18006395
Author URL: https://archiveofourown.org/users/Fukae_Flwr83/pseuds/Fukae_Flwr83
Summary: You are a sweet and kind human that just also happens to be dating the small royal guard skeleton. You are a delicate flower that is innocent of all sexuality.......NOT! You're secretly a hardcore kinky pervert who hasn't gotten the courage to tell her datemate that she isn't all that innocent. That's ok though, you've managed to get your kink frustrations out on your own time when no one is around. Except for this time, you've been caught. By Mutt. SHIIIIIIIITTTTT!!!!!!!





	It's Just You and Me Now

**Author's Note:**

> My first attempt at smut. I hope it isn't bad. I hope to make more in the future cus im garbage hehe. Please enjoy, and I apologize in advance if it is crappy.
> 
> WARNING:  
> This is a one-shot where the reader does the nasty with Mutt. There will be cheating. sorry, Sans...

You had been living with skeleton brothers for half of a year now, and dating Black for two years. You were very happy with your current life. You had met Black at work when an angry customer wasn’t happy with her food and thought it was best to take the anger out on you, even though you didn’t make it. Black was the one who got her out of your hair. It wasn’t the first time you had met a monster, but it was the first time you met a skeleton. He was shorter than you by an inch but still very much terrifying at the time. Even though you were probably scared shitless, you still felt the need to thank him, and so asked for his number. Of course, he took it as you asking him out on a date, in which he responded with a laugh. He gave you his number though, so there was that.

It kind of spun out of control after that. What was supposed to be a simple “ _thank you for saving my ass_ ” coffee meetup turned into an all-day date with Black who had gotten it into his head that you had feelings for him. You could’ve ended it there by saying you didn’t have any feelings but firstly you didn’t want to hurt his feelings because you are just that nice, and secondly….you kinda were interested.

So eventually it turned into something real and now here you are, living with the skeleton brothers. You were very happy with your relationship with Sans, and it couldn’t be better…except there was one thing. Black was secretly a gentle lover. Living in the underground where violence was practically everywhere, everyday, actual love was a rarity. It was weakness and Black was never about weakness, unless it was with you, when you were alone. He was always making sure you were well taken care of and made sure to show you affection especially when it came to sex. He treated you like his precious delicate flower that needed constant protection and you loved it, but you weren’t delicate, or all that innocent.

You would’ve told Black that you were secretly a hardcore pervert into a lot of dirty things, but you always lost your nerve and didn’t want Black to think of you differently. You were his precious innocent flower, why dirty that image and have him disgusted by you? Which is why you kept your dirty mind locked away. It was working for the past two years, though there were times where you had to do some dirty things while alone. Everything was perfect, innocent for Black and a big pervert for yourself, and no one knew.

“Y/N! I’M LEAVING NOW!” Black called out from downstairs. You immediately were pulled from your thoughts as you ran down the stairs. Black was leaving for two days on this Royal Guard Training thing with Alphys and that meant you would be by yourself with…Mutt.

You were honestly very worried about being alone with Mutt. It seemed like he has never liked you, from the moment he met you till today. You hardly talked and when you did, he always gave you simple answers. You always caught him staring at you with intense eyes. One time you had caught him sitting on the couch just watching you with very intense eyes, grinding his teeth. He even snapped his cigarette in half with his bare teeth. There something about you that seemed to tick him off, but you were always super sweet, and kind to him. You never wanted to start problems with anyone. You wanted to be friends with everyone, that’s just the kind of person you were.

As you reached the end of the stairs, you caught Mutt staring once more in his usual spot on the couch. You just shrunk into yourself, his stare causing a strange feeling in the pit of your stomach.

 _“Why does he hate me so much?”_ you whimpered in your mind. Maybe while Black was gone you could try and be friends. You went up to Black, who stood at the front door waiting for you.

“Y/N, THERE YOU ARE. I WILL BE LEAVING NOW. BE SURE TO TAKE PROPER CARE OF YOURSELF IN MY ABSENCE. I WILL BE CHECKING EACH NIGHT!” Black stated. You just smiled at him as he spoke. He really did care about you in his own ways.

“I wish you didn’t have to leave. I’m going to be so lonely,” You gave him your best sad puppy face, hoping maybe he’ll change his plans for you.

“NONSENSE! MUTT WILL BE HERE AS WELL!” Black gestured to his lazy brother on the couch. You laughed awkwardly then looked to Mutt who just eyed you then smirked. A smirk that sent certain chills down your spine. You weren’t sure if they were good or bad, but they definitely increased the strange pit feeling.

“Ha ha yeah, of course.” You turned back to your lover, unsure if you were going to survive the next two days. He wouldn’t do you in while you were sleeping right? Black would kill him if he did, and Mutt didn’t go against his brother.

“Don’t worry, darlin. I won’t bite,” He spoke with his sultry voice in a certain way that sent another wave of shudders.

**_“Imagine that voice in your ear, whispering about how amazing your pussy is as he fu…”_ **

_“NO SHUT UP!”_   You internally screamed kicking that side of your brain, “That’s Black’s brother! How could you!” You quickly pushed that dark side of you away back into the abyss before anyone noticed how messed up you were.

“I MUST BE OFF NOW!” Black announced thankfully distracting you. You gave Black a passionate kiss to his teeth, hoping to convey your nervousness. You were already forgetting why you were so anxious as you felt his hands wrap around your waist and pull you closer. You loved kissing this boney boy. His magic danced against your lips, sending a pleasant warmth all over your body. You could feel yourself getting all hot and bothered by a single kiss. Finally Black pulled away, blushing slightly but looking pretty proud of himself.

With that beautiful note, Black left you standing in front of the door, slightly hot and bothered. Thankfully the growing awkward silence between you and Mutt was quick to kill you steamy mood.

“Um,…so…what do you want for dinner?” You offered, trying to break the silence. Mutt just stared at you, before pulling out a cigarette and lighting it.

“Dunno. Whatever you want.” He responded bluntly. You just internally frowned. This was going to be a long two days.

 *   *   *

You finally got to your room that you shared with Sans, feeling tired. You and Mutt had decided on Muffet’s for dinner. It was easy and Mutt always liked take out. It was still really awkward even though you attempted at small talk with Mutt. He was so hard to understand, even more so when trying to get to know him better.

But now you were in your room, and when you left Mutt was watching some show on tv, so he was busy. You could finally release some of the pent of frustrations. You made sure to lock your door so Mutt wouldn’t walk in on you. You quickly ran to your closet and on the top shelf was your goodies. The highest shelf because It was too high for Black to reach

You had your own personal box of playthings and lingerie that was way too sexy to be worn around Black. You took your box to the bed and rummaged through it, looking for your favorite lingerie. You had gags, chokers, dildos, cuffs and other things in this sin box of yours. You really had a thing for sexy, kinky and cute styled things.

You took your lingerie from the box and ran to the bathroom, leaving your sin box out on the bed. You quickly threw on your thigh high black lacy stockings and you black garter belt. The straps were thin and delicate but hella sexy. The garter belt was all straps, had this very bondage look to it, which you loved. The idea of being tied, and fucked senseless always got you going. You attached the straps to your stockings. To you, the color black meant  _‘fuck me hard and make me beg for it’_  while white meant  _‘be gentle with my pussy, please_ ’ which you didn’t want while you were alone, obviously.

Then you put on your favorite 3d skeleton bra that pushed up your boobs in the most delicious way. You practically bit your lip in anticipation. This bra allowed you to imagine Black being completely rough with you. You looked so good so far. The underwear you chose this time was simple but cute. A lacey black pair that didn’t hide much; the bondage-like straps were what really drew you to it. The panties were low riding so most of your ass was out.

You moved to the long body mirror you and Black had in the bathroom. You brushed your hair nicely and checked yourself out. You looked like sex. All hot, yet cute, and definitely not innocent. If anyone saw you in this, they’d most likely know how much of a pervert you really were, or think you were some kind of stripper, not that you’d really mind.

After making sure you looked fuckable you exited the bathroom, now was the time to let your imagination run wild as you played with yourself, maybe even take some sexy photos to add to your sin box. Only when you reentered the bedroom, you felt your soul sink to the floor. Sitting on your bed, looking through your sin box was Mutt. You felt your entire body shatter to pieces as you ran over to the bed, and flung yourself over the box, praying he didn’t see much.

Your pride and image were gone; he was going to tell Sans how much of a dirty fucker you were and it’d be all over for you. Black wasn’t going to want to be your datemate anymore. Mutt hated you enough to ruin everything, right?

“Fucking knew it,” Mutt chuckled from above. You could feel his burning eyes on you, quickly reminding you of what you were currently wearing. You immediately placed one hand over your ass, trying to hide it. This was an absolute nightmare.

“I always knew that sweet and innocent act wasn’t real,” he stated as he got closer to your ear, his hot breath tickling the back of your neck. You shivered at the sound of his deep voice so close to your ear. You felt your eyes burning at your shame.

“Wha…what are you doing, Mutt!?” you demanded, trying to sound strong but failing. He saw your box of pleasures, and now knows how disgusting you are. How you wished you weren’t such a pervert. Why were you like this?

Instead of answering you, he let his cold hand ghost over your ass before giving it a hard squeeze. You immediately gasped and pulled yourself away from him. The tingles from the firm squeeze running amok over your body. No way this was happening. You still had your box in hand, holding it over your very much exposed stomach.

“Wh…what do you want, Papyrus!?” you hissed, feeling beyond furious. You had met him way before you moved in and even then he treated you like a plague, hardly talking to you, hardly interacting, and always staring. Now he was in your room going through your private stuff?! What the hell was his deal!?

“Just came in to check on ya,” he grinned as he rose from the bed. He took one step towards you while you took a step back, your grip tightening around the box. Why would he even bother checking up on you?! Of all the times to show some sign of caring, he chose this very moment?!

“Black know about your…toys?” he questioned with a shit eating grin. Of course, he knew Black didn’t know. You would die of embarrassment if he ever found them. you felt your throat close up on her as you tried to answer but your embarrassment took away her voice. You just looked away in shame feeling the heat in your folds. Why was this turning you on?!

“Black said he did want us to try and get closer while he’s gone,” you watched as Mutt’s eyes raked over your body, practically undressing you with his eyes. The desire in his eyes was such a turn on, but you had to fight it. This was Black’s brother! You couldn’t do that to him.

“I think I’ve got some ideas on just how we can get closer,” Mutt licked his teeth with that long wine-colored tongue of his.

 _ **“Oh that tongue could fuck us up real good,”**_  Your darker self practically moaned in your head. You just bit your lip hard fighting your stupid brain.

“I would never cheat on Black!” you declared as you finally backed up into the wall. This was bad. Mutt kept advancing towards you, looking ready to devour you. You just subtly squeezed your thighs together for some friction.  _“Stupid body! Getting all turned on by Mutt! What is wrong with me?!”_  You cursed your body for reacting in such a way. It didn’t go unnoticed by Mutt.

“I can smell your desperation, honey,” his breath coming off ragged, kissing your face. Oh god, this was so wrong but it was making you feel so hot. You felt the box slip from your hands as your knees got weak.  _“How much of a perverted slut am I?!”_  You cried in your head. You shouldn’t be this turned on but you were.

“It’s just you and me now, darling,” Mutt whispered into your ear before gently biting your earlobe. You accidentally let a pleasurable sigh escape your lips only realizing what you did a little too late. You can’t do this! Black is your boyfriend and this his brother. That was all kinds of fucked up, and yet you secretly were enjoying this too much.

You gasped when you felt him push his body against yours. It was just like Black’s, somehow muscular, strong and not boney. You chalked it up to magic. He ground into you in a way that was making you lose all rational thoughts. It felt so good, and rough. He wasn’t being gentle with each grind into you, and it was hitting you in the right spots.

“You can say whatever, darlin, but your body ‘s tellin me differently.” He groaned into your ear as your hips natural ground back against his. You just closed your eyes, focusing on the hard feeling of him pinning you to the wall with his pelvis. You bit back your whimpers, still trying to hold onto some dignity.

His hands begun to snake around your body, pulling you closer with one hand while the other moved toward your thigh. He squeezed it roughly before yanking your leg up around his waist. Your body was completely at his control at this point. With this position, he thrust himself even harder into you, sending intense waves of pleasure through you.

“Not even fighting me anymore, are you?” Mutt hissed into your ear, his voice a tad hoarse. You were turning him on, weren’t you? Somehow that thought made you even more wet for him. You having this effect on him only made everything that much better. This was not how the night was supposed to go.

You couldn’t help the small moan that escaped your lips when he roughly thrust his hips against yours in a certain way, hitting that perfect spot. You could feel his big dick rubbing against your wet core, even though he was still fully clothed. 

He was dry fucking you into the wall and you were letting him. It just felt too good for you to stop him, not that you could if you tried. You hadn’t realized you moved your arms around his neck, pulling him closer until you opened your eyes. He was still watching you intensely as he thrust even harder in that same spot. If anything his eyes were really doing it for you. The way he watched you as you came undone by him just added to everything. It wasn’t that sweet, gentle stare you often got when making love with Black. No this was the stare of a cocky bastard completely taken by desire and lust. You could feel your stomach tightening. You were so close to reaching the edge.

“Look at you. Coming panting like a bitch for me, aren’t you?” He grinned at you. You just nodded, unable to form words currently. Yes, oh absolutely. At this moment, you completely at his mercy.  He kept thrusting at a rough but calculated pace, never losing rhythm. You weren’t going to last much longer with the way things were going, and he knew this. All too suddenly he stopped everything. You practically whimpered at the loss of friction. Why did he stop?

“You can’t come, darlin. Not yet,” he winked at you before yanking your other leg up around his waist. He pulled you off the wall, and walked over to your bed, only to throw you down on it. You just got up on your elbows looking up at the tall skeleton cautiously. He was so menacing and kinda intimidating. You felt even more turned on and scared at the same time. He just smirked as he slowly removed his jacket from his body, leaving him in his black muscle tank.

“I'mma have ya screamin for me in this bed,” Mutt spoke lowly, sending shivers down your spine. You felt even dirtier than ever. This was you and Black’s bed. This was where you and Black had sex, where you slept together every night. This was so very wrong yet you could feel yourself soaking at the prospect.

“I…I can’t,” You stuttered as he crawled on top of you. His hand slipped around to the arch of your back. His cold bones giving you goosebumps on your bare skin. You were saying no, still somewhat trying to keep your sweet, innocence but your body was practically begging him for this like the perverted slut you were.

“I’m not givin’ ya a choice,” Mutt smirked before prying your legs apart with his own strong legs. You gasped slightly when you felt his hard bulge against your clothed sex once more. He just kept his eyes on you as his other hand begun to carefully run up your leg starting at your knee. His sharp fingertips pressed against your skin, leaving slight red marks as he worked his way up to your thigh. You squirmed against Mutt’s chest but he kept you still as he teased you with his hand.

You flung your hands to his tank top, clutching tightly and desperately once his tips finally reached your clitoris. You felt him rub his hand against it at an agonizingly slow pace.

“So wet for me, little fucking slut.” He chuckled rubbing harder as your hips bucked into his hand in response, “You really are the worst. Doin this kinda thing with your boyfriend’s brother, on his bed too,” He whispered just as his hand finally slipped into your panties.

He was right, and you should absolutely hate for yourself, but instead, it was turning you on more hearing him say it out loud. You moaned as he slipped one finger into and bucked your hips even more into his hand. It was so long and his magic was coating his fingers making them feel thicker than they were.

“Fuck…you’re squeezing me so tightly…” He hissed thrusting his another digit into your tight core. You gripped his shirt even tighter, even pulling him closer to you. You had your eyes closed and only focused on this feeling of him in you. You’d worry about the consciousness later, right now you needed to feed your sick desires. It had been so long since you ever had something like this, and god you needed it.

Another two digits were added and you were a moaning mess, getting a bit loud. Mutt wasn’t silencing you either, after all, it was just you two in the house. No around to hear you betray your boyfriend with his brother. Now with all his fingers deep in you, Mutt started a brutal pace, thrusting his fingers even further into you with every thrust. There was no way to fight back the moans anymore. You even threw your legs around his waist to give him better access, all the while thrusting your hips in time with his fingers.

“Ah…ha…look at you…fucking yourself with my hand. Such a dirty slut.” He nipped at your ear, his hot breath on your neck and ear. Yes, you were a slut, his slut right now. He could do anything he wanted to you, and you wouldn’t even reject him anymore. You wanted this that badly.

You felt your stomach tighten, your edge so close. It was right there! Mutt increased his pace at the feeling of how close you were, bring you to your climax that much quicker. You felt him drag his hot tongue across your neck before roughly nipping you with his fangs.

“Come for me, bitch!” He order and that was it. You moaned loudly as you felt yourself come undone on his hand. You fell back onto your bed, breathing hard. You whimpered as Mutt slowly pulled his fingers from you.

You can’t believe you just did that. Oh man, you were the absolute worst, but damn it, that was amazing. You just needed a moment to calm yourself down, but it seemed like that wasn’t going to happen. You felt Mutt remove his hand from underneath you, and move away from you, only to hear his zipper being pulled down.

Your eyes shot open and you looked to the tall skeleton standing over you. His tank was gone and his hands were slowly pulling his pants lower in a very teasing manner.

“Oh, you thought we were done?” He questioned, looking all smug about it too, “I said I was gonna have you screamin, and I meant it, babe,” He chuckled, finally removing his pants. You couldn’t help but not the incredibly large bulge in his briefs. A very large package was being held back, much larger than Black.

“Like I said, darlin. It’s just you and me for the next two days,” Mutt grinned moving closer to you, his fingers moving up both sides of your legs, towards your lacy panties, “And you are all mine.”

It was going to be a long two days.   

**Author's Note:**

> WELP hope that wasn't too horrible. If you liked it even a little bit, please kudos and some comments. This is just a one-shot broken into a couple of parts sooooo thanks for reading anyways.


End file.
